This invention relates to improvements in cassettes of the room-light load type, and in particular of the core lock known to be used in such cassettes. Such cassettes contain a web of photographic material, being wound up in a roll borne on a reel core having a longitudinal axis. The core comprises core hubs at opposite ends of the core, and being borne between two hub seats provided in opposite cassette end caps; such cassettes are known which comprise a breakable core lock adapted, while in unbroken condition, for locking at least one of the two opposite core hubs against rotation in the corresponding hub seat therefor. Of course, locking one hub against rotation in its seat means automatically locking also the other hub, unless the rotating force applied is strong enough to break the core lock. A known cassette of this type further comprises conventionally a casing having a light-tightly sealed web exit slot, so that, when the core lock is broken at a desired breaking site provided therein, the core hubs and together therewith the core and the roll of photographic material thereon can be easily rotated in their hub seats and a desired length of the web of photographic material can be unwound from the roll and can be exited through the cassette slot.
The term "room light" is understood to include daylight as well as artificial lighting.
A day light cassette having the above described features has been described in European patent application No. 0 053 856 and comprises cassette end caps containing hub parts which protrude into the two ends of the roll-bearing core and are firmly joined to its internal side. In the interior of the reel core there is clamped in a flat closure part which extends along a central longitudinal plane and is connected with a flat head part by means of a narrow connecting part which is to serve as a desired breaking zone. When assembling the known cassette, the head part is inserted in a slot which is located in a wall section of the hub part. When, after conveying and handling the known daylight cassette, the photographic material is to be exited therefrom, it must be pulled out of the cassette with an initial pulling force of about 30 Newtons.
This subjects the photographic material to considerable stress and may easily damage the same. When assembling the known daylight cassette, an exact orientation of the reel core containing the set-in flat closure element is required to correspond with the location of the above-mentioned slot so that the head part of the closure element will be located exactly opposite that slot when the various parts are being put together.
In an article in "Research Disclosure", volume 4244, Nr. 163 of November 1977, there is described under No. 16352 on page 43 a core locking device having a radially displaceable core locking member which engages, when in advanced position, a groove or slot of a web-winding core and prevents the core from rotating. In order to free the core lock, the locking member of the locking device, which comprises a considerable number of parts, must be displaced radially outwardly. This does indeed avoid subjecting the photographic material to stresses when changing to the free position; however, the known locking device requires numerous parts whose manufacture is complicated and which are difficult to assemble.
In U.S. Pat. No. 3,613,880 to Perrin there is described a dispenser containing a roll of strip material such as paper toweling wound up on a rotatable core. At one end the core bears a trunnion having a disk flange with triangular teeth projecting axially from the disk face turned away from the core. These teeth penetrate into a wall of the carton containing the paper roll for shipping, in order to prevent shifting of the roll in the carton. After shipping, a roll is taken out of the carton and placed in a dispenser having a rotatable disk-shaped support member. The trunnion end is rotatably locked with the support member by axially inserting the trunnion teeth into matching gaps between teeth, of trapezoidal cross section, in the periphery of the support member. The arrangement of the trunnion and support member does, however, not serve as a core lock, and could not be used as such, for a core bearing a roll of light-sensitive photographic material as the latter must, of course, not be removed from the cassette containing the same. The support member rotates freely.
Cassette end caps of reduced wall thickness and having various projecting areas and recesses for guiding a cassette hull during assembly with the end caps have been described in European patent application No. 0 016 488.
Finally, in U.S. Pat. No. 4,272,035 to Sherman et al, there is described a room-tight load cassette for light-sensitive strip material having a dispensing slot which is sealed to be light-tight by a layer of plush adhering to a profiled bar which is inserted into a slitted portion of the cassette wall and contacts a similar strip of plush on the opposite cassette wall adjacent the slot. No core lock is provided.